Manufacture of high octane gasoline



Feb. 13, 1945. F. J. JENNY MANUFACTURE OF HIGH OCTANE GASOLINE Filed Oct. 30, 1941 ATTORNEY Patenfd Feb. 13, 1945 MANUFACTURE 0F HIGH oo'rANE l GAsoLrNE Frank J. Jenny, Forest Hills, N. Y., asslgnor to The M.W. Kellogg Company, J crsey City, N. J., aV corporation ofv Delaware Application october 3o, 194i, serial No. 417,054

3 Claims. "(Cl. Zim-683.4),

. lThis invention relates to the manufacture 0f high octane gasolinel and particularly tOan improved combination of gasoline manufacturing processes including naphtha reforming, butane pyrolysis, and catalytic iso-parafn-olen alkylation'. The invention has for its principal object the provision of a method of pyrolyzing the nonalkylatable hydrocarbon normal butaner to produce the alkylatable hydrocarbon butylene, and

-of simultaneouslyA thermally reforming a low octane naphtha, wherein the normal butane treatment contributes to the efiiciency ofthe naphtha reforming step. Other objects and advantages of the invention will appear during the course of the description hereinafter given.

V In order to achieve the foregoing and related ends it is contemplated by my invention to pyrolyze butane at a high temperature to .produce butylene, and to. reform a naphtha to a substantial extent, and then to combine the hot pyrolysiS products with the naphtha. The combined streams are then subjected briey to relatively severe reforming conditions to enhance further the antiknock properties of the naphtha. I have vfound that when naphtha is reformed in thepresence of light normally gaseous hydrocarbons, a higher reforming temperature may be usedwithout excessive coke formation, and hence a higher octane product may be produced. During early stages of the naphtha reforming conversion, when severe temperature conditions have not been reachedand while the more' readily reformable fractions are being converted, there is no important advantage to be obtained by having light hydrocarbons present. It is for this reason `that I a'dmiX pyrolysis products with naphtha which has. already undergone 'substantially the usual lextentof reforming, so as to make possible further conversion under especially severe conditions which normally are deposition." i f Proper temperatures for' butane pyrolysislie n the' vicintyof 1050 F. and higher, 'While naphtha reforming as ordinarily practicedv employs temperatures between about 950 F.Y and 10257 F.' It is contemplated by the; invention that hot pyrolysis products, at a temperature of about 1050" F. or higher, sha1l be mixed with naphtha which has been reformed at about 1000" F, to 1(1 2 5 f F. Upon being commingled with the pyrolysisproducts, the naphthais givenasubstantial instantaneous temperature increase., and during further heat treatment vof vthe mixture-as contemplated bythe invention it is enabled to with.;

productive of excessive cokel ine excessive amounts of' coke,A by. reason of the presence ofthe light normally gaseous pyrolysis products` Subsequent to this further heat treat'- ment in accordance with additional features of my invention I recover high octane gasoline produced by ythe naphtha reforming operation; I'

also recover butylene produced by the pyrolysis together with C4 hydrocarbon by-products of thel reforming, including iso-butane. I subject-the latter materials, augmented if' desired with additionaljalkylatable C4 hydrocarbons, to .catalytic yalkylation, whereby 'I produce further amounts4 of high octane gasoline.

A preferredv embodiment of the invention will now be described in detail with reference to the annexed drawingx which isa diagrammatic flow sheet. It is to be understoodlhowever, that this embodiment is villustrative only, and in no way limits the scope ofthe invention. l

In thedrawing,A naphtha whichis to be treated in accordance with .the invention is taken from r any suitable source'and passed through line l into a preheating coil 3 located in the convection section of a furnaceZ, and passes thence to a vv'tane' (derived from a subsequent step of the process) traversing line l6. The combined normal butane' stream goes through line 6 intol a preheater=coil1 situated inthe convectionseotion of furnace 2 and from thence entersa'pyrolyd sis coil 8 situated in a radiant section of the fur` nace. vUpon entering the pyrolysis coil the bustand the increasedftemperaturewithout deposite. so

tane stream mayl be suitably at a temperature of approximately 900 F.- and in' traversing the pyrolysis coil is heated to a temperature which is preferably about 1050* F. to 1250Q F. -At this high .temperature the normal butane is partially converted into butylene, the by-products being and lighter hydrocarbons.4 After traversing coil 8 the stream is ladnlxedwith. naphtha from coil tand the commingle'dstreams are then passed through a further soakingcoil 9 infwhich a tem-- perature of about 1025 F, to10501i. ismain"l tained, During its traverse; of-this soakingcoil further `reforming of the naphtha takes `place with the result that the octane number thereof is substantially increased.

On leaving the soaking coil 9 the hot conver-l sion products travel via line I I into a bubble tower I2 wherein, by appropriate fractionation under refiux, any by-product material boiling above the gasoline range including polymer and tarry residue is separated andwithdrawn asindicated by line I3 for disposal as desired. Gasoline fractions and normally gaseous hydrocarbons are taken overhead from bubble tower I2 via line .I4 and are further fractionated in a debutanizer I5 from which gasoline fractions are withdrawn as indicated by line I6. The gasoline so withdrawn com` prises chiefly the product ofthe .reformingoperation on the initial low octane naphtha. Hydrof tion in the debutanizer 21. The normal butane so returned will also include such normal butane as may be formed from the .fresh feed naphtha as a by-product of the reforming operation.

Insofar as butylene yield is concerned, the most advantageous pressure at which to pyrolyze the normal butane is atmospheric. It is usually more economic to employ a moderate superatmospheric pressure, however, in order to reduce the volume ,of the material and enable a smaller, pyrolysis coil to be used. The reforming operation is best conducted at a pressure between about 500 and 1000 pounds per square inch. As a compromise pressure suitable for both types of conversions, and in order to prevent polymerization as hereinafter discussed, I prefer to use 400 to 500 pounds carbons lighter than pentane Aare preferably..

-wholly withdrawn in the overhead product from debutanizer I5 and passed Via line Il into detherein subjected in knownmanner to catalytic V alkylation in the presence of a catalyst such as y96% sulphuric acid, whereby alkylation of the `iso-butane with butylene iseffected. Although Y appreciable quantities of. iso-butane will normally be produced as a by-r-product of the naphtha conversion, the available butylene will ordinarily be more than sufficient in amount to react with all the iso-butane so produced, and it will therefore f be desirable to supply additional iso-butane to the alkylation process from an extraneous source, as indicated by line 20. Normal butane and excess iso-butane pass unchanged through the alkylation reaction, the excess iso-butane being present as a result of ,the iso-butane recycling procedure described immediately below. A's is wel1 known, catalytic alkylation of iso-butane with butylene is advantageously accomplished in the presence of a substantial excess of iso-butane.

The gross product of vthe alkylation process is passed through line 24 to a de-isobutanizer 25 from which excess iso-butane in the gross product is withdrawn overhead and returned through line'23 to the alkylation zone. The quantity of iso-butaneA so recycled for the purpose of maintaining an excess thereof in the alkylation zone is constant and does not affect the net; transfer vof materials to and from the alkylation process. Materials heavierv than iso-butane, consisting essentially of alkylate and normal butane, are withdrawn as a bottom product fromthe de-isobuytanizer 25 and pass through line 26 to a debutanizer 21 wherein nal separation of alkylate ,from lighter hydrocarbons is effected. The alkylate is withdrawn from thebottcm of the debutanizerthrough line 28 anci disposed of as desired while lighter materials, consisting essentially of normal butane,-is returned through line 6 for admixture with the fresh feed normal butane entering li'ne 3 as previously described. l

.As will be understood by those skilled in the art of hydrocarbon kpyrolysis, the conversio-n of normal butane into butylene and lighter by-pro-ducts is incomplete in a single pass through the pyrolysis coil. The maximum .yield of butylene is ultimately obtained by Dc'zontinu'olus returnof. unconverted normal butane' from" the 'final sparain coils 8 and 9. g,

, As is well known,` the pyrolysis of butane to form butylene is likely to be attended. by moreI or less polymerization of the butylene after formation thereof. My invention is distinguishable from prior known processes to which .it bears a superficial resemblance by the left that polymerization is definitely not desired and is" curtailed as far as possible by appropriately chosen operating conditions. So-called naphtha reversion processes as heretofore proposed rhave involved the use of pressures in excess of 11000 pounds per square inch and extended soaking of naphtha-olef'lnmixture's at polymerizing temperatures after formation of the oleins by `pyrolysis at higher temperatures. In such processes a complete conversion of olefns into poly- Amers of the gasoline type is aimed at. Polymerization in the pyrolysis coil 8 is substantially l.prevented bythe maintenance of a more or less continuously risingtemperature gradient therethrough and by the relatively low pressure. Polymerization in the soaking coil 5 is also minimized by the relatively low pressure and by making the time of residence of the material therein relatively brief. The` brevity of the soaking time of course limits the extent to which the naphtha can be further converted in the nsoaking coil, but by accomplishing the major portion of the naphtha conversion prior to adrnixing pyrolysis products therewith, only thev f most difficult and coke-producing conversion remains to be effected in the soaker. high temperature Aof the soaking fcoil the naphtha reforming reaction vgoes on relatively rapidly as compared to the v polymerization reaction lsoughtto be avoided. Y yIt is to be understood that arrangements other than the one described herein for illustrative purposes may be devised within the scope of'my invention, which is limited only by the following claims.

`I claim:

1.'A` hydrocarbon conversion process which comprises subjecting a naphtha of low antiknock value to a thermal reforming treatment, separately subjecting normal. butane to a therma1 treatment at a'pres'sure not substantially higher than 500 poundsv per square inch at a temperature higher than that employed `in said naphtha reforming treatment to convert said normal butane to butylenes and lighter hydrocarbons, the reaction time in said butane treatment ybeing restricted to minimize polymerization reactions, mixing the hot products vof said thermal conversion treatments, subjecting the resultingmixture to further thermal treatment pounds perl square'inch at a' temperature higher than that employed in said naphtha reforming treatment and above 1000 F., cooling the mixture to terminate said last-mentioned thermal treatment prior to any substantial polymerization of olens formed in said thermal treatment of butane, separating from the reaction products a low boiling fraction containing butylenes and unreacted normal butane, subjecting said frac,- tion containing butylenes and normal butane to alkylation treatment to effect alkylation of butylenes With an iso-paraiiin hydrocarbon, fractionating the products of alkylation to separate therefrom a, fraction essentially consisting of normal butane, and recycling said normal normal butane to butylenes and lighter hydroi carbons, the reaction time in said butane treatment being restrictedto minimize polymerization reactions, mixing the hot products of said thermal conversion treatments, subjecting the resulting mixture to further thermal treatment at a pressure not substantially higher than 500' pounds per square inch at a temperature higher than that employed in said naphtha reforming treat-ment, and above 1000 F., cooling the mixture to terminate said last-mentioned thermal treatment prior to any substantial polymerization of olens formed in said thermal treatment of butane, separating from the reaction products a low boiling fraction containing butylenes and unreacted normal butane, combining said fraction containing butylenes and normal butane with isobutane, subjecting the resulting mixture to alkylating conditionsy to effect alkylation of butylenes with isobutane, fractionating the alkylation reaction products to separate therefrom a fraction consisting essentially of normal butane, and recycling said normal butane frac'- tion to said thermal treatment of normal butane.

'3. A hydrocarbon conversion process which comprises subjecting a naphtha of low antiknock Value to a thermal reforming treatment, separately subjecting normal butane to a thermal treatment at a temperature higher than that employed in said naphtha reforming treatment and at a pressure not substantially higher than 500 lbs. per square inch to convert said normal butane to butylenes and lighter hydrocarbons, the reaction time in said butane treatment being restricted to prevent substantially the occurrence of polymerization reactions, mixing the hot products of said thermal conversion treatments, subjecting the resulting mixture to further thermal treatment at a temperature higher than'that employed in said naphtha reforming treatment and above 1000 F. and at a pressure not substantially higher than 500 lbs.

. per square inch, cooling the mixture to terminate said last-mentioned thermal treatment prior to any substantial polymerization of olens formed in said thermal treatment of butane, separating from the reaction products a low boiling fraction containing butylenes and unreacted normal butane, transferring said fraction containing butylenes and normal butane to an alkylation process, treating said lastmentioned fraction in said alkylation process to alkylate said butylenes with an isoparafiin hydrocarbon and separate a fraction essentially consisting of normal butane, and recycling said normal butane fraction to said thermal treatment of normal butane.-

FRANK J. JENNY. 

